Here is another solution.. how was the first ?? I have not tested this
extensively just for some sample values and it worked fine....
ciao,
anubhav
--------program code
#include<stdio.h>
int numbitset(unsigned int x,unsigned int y)
{
unsigned int a=0;
unsigned int b=0;
register int asetbit=0;
register int bsetbit=0;
for(;x>0 || y>0 ; x >>= 1, y >>= 1)
{
a = x & 01;
printf("a=%d\n",a);
b = y & 01;
printf("b=%d\n",b);
if( (a^b) && (a))
asetbit++;
else if ((a^b) && (b))
bsetbit++;
else
;
}
return asetbit - bsetbit;
}
int main(void)
{
int i,j;
printf("enter first number: ");
scanf("%d",&i);
printf("enter secon number: ");
scanf("%d",&j);
printf("difference of bits set in %d and %d = %d\n",i,j,numbitset(i,j));
return 0;
}
--------program code ends
-----Original Message-----
From: Glynn Clements <[EMAIL PROTECTED]>
To: Anukool Lakhina <[EMAIL PROTECTED]>
Cc: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Date: Tuesday, April 06, 1999 10:14 AM
Subject: Re: Another bit question
>
>Anukool Lakhina wrote:
>
>> Given two 32-bit numbers, I want to decide which number has more bits
set.
>> And what the difference in the number of bits set is. So for example, if
>> Num1=1110000...011 and Num2= 0000011...001, I'm trying to write an
efficient
>> function numBitsSet() that returns 2 if Num1 has 2 more bits set than
Num2
>> and -2 if Num2 has 2 more bits set than Num1. In this case, it'll return
2.
>>
>> Yes, I can do this easily by looping through the two numbers and storing
a
>> counter etc etc. But I need an efficient way to do this - I'm trying to
do
>> this by using a combination of xors or something. Please email me if you
>> have any suggestions.
>
> static const unsigned char count[0x100] = {
> 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
> 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
> 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
> 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
> 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
> 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
> 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
> 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
> 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
> 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
> 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
> 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 8, 8,
> };
>
> static int numBits8(unsigned int x)
> {
> return count[x & 0xff];
> }
>
> static int numBits(unsigned int x)
> {
> return numBits8(x >> 24) +
> numBits8(x >> 16) +
> numBits8(x >> 8) +
> numBits8(x);
> }
>
> int diffBits(unsigned int a, unsigned int b)
> {
> return numBits(a) - numBits(b);
> }
>
>--
>Glynn Clements <[EMAIL PROTECTED]>
